/*
 * Copyright (C) Eric Zhang.
 * 参考学习时的资料
 * http://blog.codinglabs.org/articles/intro-of-nginx-module-development.html
 * 非原创，侵删。
 */

#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>

/* Module config */
typedef struct {
    ngx_str_t   ed;
} ngx_http_echo_loc_conf_t;

static char *ngx_http_echo(ngx_conf_t *cf, ngx_command_t *cmd, void *conf);
static void *ngx_http_echo_create_loc_conf(ngx_conf_t *cf);
static char *ngx_http_echo_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child);

/* Derectives */
static ngx_command_t ngx_http_echo_commands[] = {
    { ngx_string("echo"),
        NGX_HTTP_LOC_CONF | NGX_CONF_TAKE1,
        ngx_http_echo,
        NGX_HTTP_LOC_CONF_OFFSET,
        offsetof(ngx_http_echo_loc_conf_t, ed),
        NULL },

    ngx_null_command
};

/* Http context of the module */
static ngx_http_module_t ngx_http_echo_module_ctx = {
    NULL,   /* preconfiguration */
    NULL,   /* postconfiguration */
    NULL,   /* create main configuration */
    NULL,   /* init main configuration */
    NULL,   /* create server configuration */
    NULL,   /* merge server configuration */
    ngx_http_echo_create_loc_conf,  /* create location configuration */
    ngx_http_echo_merge_loc_conf,   /* merge location configuration */
};

/* Module */
ngx_module_t ngx_http_echo_module = {
    NGX_MODULE_V1,
    &ngx_http_echo_module_ctx,  /* module context */
    ngx_http_echo_commands,     /* module directives */
    NGX_HTTP_MODULE,            /* module type */
    NULL,                       /* init master */
    NULL,                       /* init module */
    NULL,                       /* init process */
    NULL,                       /* init thread */
    NULL,                       /* exit thread */
    NULL,                       /* exit process */
    NULL,                       /* exit master */
    NGX_MODULE_V1_PADDING
};
/* Handler function */
static ngx_int_t
ngx_http_echo_handler(ngx_http_request_t *r)
{
    ngx_int_t                    rc;
    ngx_buf_t                   *b;
    ngx_chain_t                  out;
    ngx_http_echo_loc_conf_t    *elcf;

    elcf = ngx_http_get_module_loc_conf(r, ngx_http_echo_module);
    if (!(r->method & (NGX_HTTP_HEAD|NGX_HTTP_GET|NGX_HTTP_POST))) {
        return NGX_HTTP_NOT_ALLOWED;
    }
    r->headers_out.content_type.len = sizeof("text/html") - 1;
    r->headers_out.content_type.data = (u_char *)"text/html";
    r->headers_out.status = NGX_HTTP_OK;
    r->headers_out.content_length_n = elcf->ed.len;
    if (r->method == NGX_HTTP_HEAD) {
        rc = ngx_http_send_header(r);
        if (rc != NGX_OK) {
            return rc;
        }
    }
    b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t));
    if (b == NULL) {
        ngx_log_error(NGX_LOG_ERR, r->connection->log, 0, "Failed to allocate response buffer.");
        return NGX_HTTP_INTERNAL_SERVER_ERROR;
    }
    out.buf = b;
    out.next = NULL;
    b->pos = elcf->ed.data;
    b->last = elcf->ed.data + (elcf->ed.len);
    b->memory = 1;
    b->last_buf = 1;
    rc = ngx_http_send_header(r);
    if (rc != NGX_OK) {
        return rc;
    }
    return ngx_http_output_filter(r, &out);
}

static char *
ngx_http_echo(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
    ngx_http_core_loc_conf_t    *clcf;

    clcf = ngx_http_conf_get_module_loc_conf(cf, ngx_http_core_module);
    clcf->handler = ngx_http_echo_handler;
    ngx_conf_set_str_slot(cf, cmd, conf);
    return NGX_CONF_OK;
}

static void *
ngx_http_echo_create_loc_conf(ngx_conf_t *cf)
{
    ngx_http_echo_loc_conf_t *conf;

    conf = ngx_palloc(cf->pool, sizeof(ngx_http_echo_loc_conf_t));
    if (conf == NULL) {
        return NGX_CONF_ERROR;
    }
    conf->ed.len = 0;
    conf->ed.data = NULL;
    return conf;
}

static char *
ngx_http_echo_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
{
    ngx_http_echo_loc_conf_t    *prev = parent;
    ngx_http_echo_loc_conf_t    *conf = child;

    ngx_conf_merge_str_value(conf->ed, prev->ed, "");
    return NGX_CONF_OK;
}
